Two students were sexually assaulted over the weekend, one in the Coronado Residence Hall and the other while at an agricultural fraternity.

Also, two students, a boyfriend and girlfriend, were assaulted at another fraternity.

The University of Arizona Police Department kept the news of last weekend's string of incidents quiet as the cases are still in the initial phase of investigation.

The 18-year-old student in the Coronado Residence Hall told officers on Sunday afternoon that between the hours of 12:30 a.m. and 2:30 a.m., another student whom she knew sexually assaulted her inside her dorm room, said Cmdr. Kevin Haywood, UAPD spokesman.

Haywood said police have identified the suspect and are completing preliminary investigations before they interview him.

He added that the victim told police she put up a fight, actually throwing him off of her at one point during the assault. She also repeatedly screamed for him to stop, Haywood said.

The other sexual assault occurred on a 20-year-old student at the Alpha Gamma Rho Fraternity, 638 E. University Blvd. She told police on Sunday that she was sexually assaulted on Friday night or early Saturday morning by someone during a party. She knew the person by his first name, Haywood said.

Haywood said the woman and the suspect were playing pool on Friday before she left to go to the bathroom. The suspect followed her upstairs to the bathroom where the assault occurred.

The woman told police she only had a vague description of what the suspect looked like. Haywood said detectives are working with her to generate a composite sketch. He added that the suspect may not be a student or from Tucson.

While Haywood said both incidents do involve alcohol, it isn't a factor.

"In both situations they were coherent. We're focusing on the assault and not the alcohol," he said.

Haywood said police believe that no other drug was used during either incident.

The aggravated assault occurred Friday at the Delta Tau Delta Fraternity, 1550 N. Vine Ave., when a 19-year-old student entered the house and found an unknown man assaulting his 19-year-old girlfriend who is also a student. The male student attacked the suspect, but was also beaten badly, Haywood said.

The Tucson Fire Department was called to the house to treat the two, but they asked that police don't respond. Paramedics demanded that police secure the scene before they entered the house, Haywood said.

Tucson Fire officials could not be reached for comment.

The two were taken to University Medical Center where the woman was treated for, among other things, a broken hand and a cut to her mouth. Her boyfriend was treated for unknown injuries, Haywood said. They couldn't give a good description of the subject on the day the incident was reported. Haywood said detectives are working to create a composite sketch.

None of the three incidents are related, Haywood said.

Police believe that no weapon was used by the suspect during the incident.